What would you say about this person?

So we have a teammate who has been working with us for last one and half year.

Here are a few observations that we had

This person is full of himself: Always talks highly of himself as if he's jack of all trades. Always pitches in everything even if what he says does not make any sense or is factually or logically wrong. Sometime he even repeats the same thing over and over even after reminding that he has done that N number of times. Tells the same story to every new person he encounters and also changes facts while telling the story to make it look like how his opinion was/is better than everyone else. Makes fun of anyone ( Specially in front someone new) repeatedly who makes a mistake or does something unintentionally wrong even though he has done the same thing.(Example: Another teammate accidentally scratched his car with another while getting out of parking, whereas this person has rammed his car totally into another in the same parking lot. He admits it as a newbie mistake and now that he has been driving for 5 months he is a pro and the person scratching has been driving for like 4 years is a noob). Whatever product he owns ultimately becomes superior and how others are inferior and their cons(Example: His Iphone X which he bought about a month back is superior that that of another person who bought the same device 5 months back).

Always talks about money: Even if we are not interested he would always talk how much money he has, how costly the gifts were, how much money his father would be getting upon retiring from the military. All the facts do not coincide as we know how much he makes and from my own dad's retirement (Same rank a year ago) know how much money he'd be getting. His roommate who happens to work in the same organisation but in different department told her girlfriend who happens to be working in our department the amount of loan this person has taken from him and how he spends all his salary in the first 5 days. Always talks about how he bought a car and a house which our source(roommate) says belongs to his brother who does not have enough parking space.

The thought of asking this question came to mind when we were having lunch today and apparently everyone had the same observation. Its come to the point where everyone has started ignoring this person which is hampering our day to day workplace and social activity. Many have tried to tell him this bluntly but he has a high pitch voice and always has a counter answer which is very insulting in nature.

His roommate says he doesn't do any of the above mentioned with him or people in his close circle and was himself surprised when told about this.

What could be the reason of such behaviour?

He is insecure.

I agree with Nicole, my first thought was that he is very insecure, socially awkward, and trying to make a big deal out of himself to earn admiration. He's trying to fluff himself up to look good because he feels subpar or he thinks that being seen as better than he is will make him friends or get him respect or whatever.

I believe he would have to deal with his insecurities himself and there is nothing much we could do in that regards.
We just agree to whatever he says and slide out for our own mental stability.

Anything we could do from our side to stop this?